Apparatus and method for chemical/mechanical polishing

ABSTRACT

A polishing pad is fixed on a polishing platen mounted to be rotatable. An abrasive supply tube supplies an abrasive onto the polishing pad. A substrate holder is mounted to be rotatable above the polishing pad, holds a substrate to be polished and presses the substrate against the polishing pad, thereby polishing the substrate. A dresser is mounted to be rotatable above the polishing pad, and dresses the polishing pad. A torque detector detects the rotation torque of the polishing platen or the rotation torque of the substrate holder. A dresser controller makes the dresser dress the polishing pad if the rotation torque detected by the torque detector is equal to or smaller than a predetermined value.

BACKGROUND OF THE INVENTION

The present invention relates to apparatus and method forchemical/mechanical polishing for planarizing the surface of a film,such as a conductor film or an insulator film, deposited on asemiconductor substrate in multilevel interconnect and/or elementisolation processes of a semiconductor integrated circuit.

Chemical/mechanical polishing (CMP) enables global planarization of asubstrate, which cannot be accomplished by any other planarizationtechnique such as resist etch-back. Thus, CMP is one of most noticeableplanarization techniques suitably employed for fabricating asemiconductor integrated circuit being miniaturized day by day. Inaddition, by performing CMP, various problems, such as inaccurateexposure resulting from the variation in depths of focus during alithography process and inferior reliability of wires formed on anon-planarized surface, can be solved.

A conventional chemical/mechanical polishing apparatus (hereinafter,simply referred to as a “CMP polisher”) will be described with referenceto FIG. 10. FIG. 10 is a schematic representation illustrating anarrangement for a conventional CMP polisher.

As shown in FIG. 10, a substrate 1 to be polished, made of silicon orthe like, is held by a substrate holder 2, which is rotatable andvertically movable. A polishing pad 3 for polishing the surface of thesubstrate 1 is attached to the planar surface of a polishing platen 4for moving rotationally. An abrasive (in a slurry state) 5 is suppliedthrough an abrasive supply tube 6 every time by a predetermined amountand dripped onto the polishing pad 3.

In the CMP polisher having such an arrangement, when the polishingplaten 4 is rotated with the abrasive 5 dripped through the abrasivesupply tube 6 onto the polishing pad 3, the polishing pad 3 is alsorotated correspondingly. And when the substrate holder 2 is brought downwhile rotating, then the substrate 1, held by the substrate holder 2,comes into contact with the polishing pad 3. As a result, the surface ofthe substrate 1 is polished. The CMP polisher shown in FIG. 10 includesa single substrate holder 2. Accordingly, the polisher is of the typepolishing a single substrate 1 during a single polishing process step.Alternatively, if a CMP polisher having a plurality of substrate holders2 is used, then a plurality of substrates 1 can be polished in parallelwith each other during a single polishing process step.

However, if polishing is performed by getting a large number ofsubstrates 1 into contact with the polishing pad 3 one after another,then the polishing surface of the polishing pad 3 gradually loses itscapacity to hold the abrasive 5. This is because as polishing isperformed for a longer and longer time, the polishing surface of thepolishing pad 3 gets more and more clogged owing to the deposition ofpolishing debris, the mass of abrasive particles and the like. As aresult, the amount of the abrasive 5, held in a polishing region wherethe polishing pad 3 and the substrate 1 are in contact with each other,decreases, and consequently the number of abrasive particles containedin the abrasive 5 also decreases. Accordingly, a rate at which thesubstrate 1 is polished (hereinafter, simply referred to as a “polishingrate”) adversely decreases.

Thus, it is necessary to re-increase and stabilize the polishing rate byrejuvenating the clogged polishing pad 3 through dressing. “Dressing” isa process step for recovering the polishing pad's 3 capacity to hold theabrasive 5 by eliminating clogging from the polishing pad 3. Cloggingcan be eliminated, for example, by rotating and pressing a dresser 7, towhich fine particles of diamond or the like are embedded, against thepolishing pad 3. If dressing is performed at regular intervals, then thepolishing rate for a substrate can be increased and the variation inpolishing rates among substrates can be reduced.

In general, the dressing process step is performed every time a numberof substrates have been polished over a predetermined amount of time orevery time the number of substrates polished has reached a predeterminednumber. Also, the dressing process step is performed either in parallelwith the polishing process step of a substrate or in an interval betweenthe polishing process steps of substrates.

The amount and number of abrasive particles, which exist on a polishingpad and contributing to polishing, are variable depending upon theroughness of the polishing surface of the polishing pad. Accordingly,the polishing rate of a substrate is also considerably affected by thevariation in roughness of the polishing surface of the polishing pad.Thus, in order to keep a polishing rate constant, the roughness of thepolishing surface of the polishing pad is desirably kept constant.

However, no method has heretofore been suggested for sensing theroughness of the polishing surface of a polishing pad. Accordingly, asdescribed above, dressing is performed every time a number of substrateshave been polished over a predetermined amount of time or every time thenumber of substrates polished has reached a predetermined number.

Since the roughness of the polishing surface of a polishing pad cannotbe kept constant, various inconveniences are very likely to occur in thecase of sequentially polishing a large number of substrates. Forinstance, the polishing rates are gradually decreased or varied amongthe substrates because the polishing pad gets clogged. Also, since thesurface of the polishing pad is glazed, trouble tends to happen intransporting a substrate being held on a substrate holder. Specifically,it becomes less easy to take away the substrate from the polishing pad.

SUMMARY OF THE INVENTION

In view of the above-described problems, the present invention was madeto reduce the variation in polishing rates among substrates by sensingthe roughness of the polishing surface of a polishing pad and byadaptively dressing the polishing pad in accordance with the roughnesssensed.

The present inventors supposed that the roughness of the polishingsurface of a polishing pad might be sensed based on the rotation torqueof a polishing platen on which the polishing pad is fixed. Based on thissupposition, we examined the relationship between the polishing rate ofa substrate and the rotation torque of a polishing platen from variousangles. Herein, the rotation torque of a polishing platen is moment offorce about the rotation axis of the polishing platen. Assume theposition vector at a point about the rotation axis to be r and thevector of rotational driving force starting from the point to be A.Then, the rotation torque T is given by the vector product of r and A,that is to say, T=r×A.

In chemical/mechanical polishing, the magnitude of the position vector ris constant, while the magnitude of the rotational driving force vectorA is proportional to the frictional force between a polishing pad and asubstrate. And the direction of the rotational driving force vector A isaligned with the direction of rotation of the polishing platen, i.e.,the rotation direction of the polishing pad. Thus, the rotation torqueof the polishing platen is proportional not only to the magnitude of therotational driving force vector A but also to the frictional forcebetween the polishing pad and the substrate. Accordingly, if therotation torque of the polishing platen is monitored, then thefrictional force between the polishing pad and the substrate andtherefore the roughness of the polishing surface of the polishing padcan be sensed nondestructively and instantaneously.

FIG. 11 illustrates the waveform of a signal obtained by quantifying therotation torque (i.e., a rotation torque signal waveform) of a polishingplaten during the polishing process step of a single substrate. In thisexample, dressing is performed on a polishing pad just before thepolishing process step of the substrate is started. As can be understoodfrom FIG. 11, immediately after polishing is started, large rotationtorque is obtained thanks to the effect of dressing on the polishingpad. As polishing is performed for a longer and longer time, the effectof dressing attenuates. As a result, the rotation torque decreases to acertain magnitude. However, if an abrasive is continuously supplied, asufficient amount of abrasive (i.e., a sufficient number of abrasiveparticles) continuously exists on the polishing surface of the polishingpad. Consequently, rotation torque of constant magnitude is maintained.The rotation torque is a vector and thus has a direction. In FIG. 11,the rotation torque signal waveform is located on the negative domain.This is because the direction of rotation of the polishing platen isclockwise with respect to that of the polishing pad. The direction ofrotation torque has nothing to do with the frictional force between thepolishing pad and the substrate. It is the absolute value of rotationtorque that does have something to with the frictional force.Accordingly, in this specification, the magnitude of rotation torque isrepresented by the absolute value thereof.

FIG. 12 illustrates the rotation torque signal waveforms of a polishingplaten where a plurality of substrates are sequentially polished oneafter another and where dressing is performed on the polishing pad justbefore polishing of a substrate is started. As shown in FIG. 12, therotation torque signal waveforms of the polishing platen for respectivesubstrates have amplitudes gradually decreasing as the continuouspolishing process for the substrates proceeds. In other words, as thecontinuous polishing process is performed for a longer and longer time,the rotation torque gradually decreases. The rotation torque decreasespartly because the number of abrasive particles contributing topolishing decreases as the polishing surface of the polishing pad getsmore and more clogged.

FIG. 13 illustrates the relationship between the number of substratesprocessed and a polishing rate. Herein, the polishing rate means adecrease in thickness of a film in a predetermined amount of time. Ascan be understood from FIG. 13, as the continuous polishing processadvances, the polishing rate decreases. The decrease in polishing ratescorresponds to the decrease in amplitudes of the rotation torque signalwaveforms shown in FIG. 12. In polishing a large number of substratesone after another, the polishing surface of the polishing pad gets moreand more clogged as the polishing process advances. As a result, therotation torque decreases, and the polishing rate also decreasescorrespondingly.

The present invention was made from these points of view. Specifically,the present invention is embodied in the apparatus and method forchemical/mechanical polishing summarized below.

A first chemical/mechanical polishing apparatus according to the presentinvention includes: a polishing platen mounted to be rotatable; apolishing pad fixed on the polishing platen; abrasive supply means forsupplying an abrasive onto the polishing pad; a substrate holder,mounted to be rotatable above the polishing pad, for holding a substrateto be polished and pressing and polishing the substrate against thepolishing pad; a dresser, mounted to be rotatable above the polishingpad, for dressing the polishing pad; torque detection means fordetecting at least one of the rotation torque of the polishing platenand the rotation torque of the substrate holder; and dresser controlmeans for making the dresser dress the polishing pad if the rotationtorque detected by the torque detection means is equal to or smallerthan a predetermined value.

In the first chemical/mechanical polishing apparatus, when clogging isgenerated in the polishing surface of the polishing pad after a certainnumber of substrates have been polished one after another, the rotationtorque detected by the torque detection means becomes a predeterminedvalue or less because of the decrease in frictional force between thesubstrate and the polishing pad. Then, the dresser control means drivesthe dresser to dress the polishing pad. As a result, clogging can beeliminated from the polishing surface of the polishing pad and theamount of the abrasive interposed between the substrate and thepolishing pad can be increased. Accordingly, it is possible to preventthe polishing rate from decreasing and to eliminate the variation inpolishing rates among the substrates.

A second chemical/mechanical polishing apparatus according to thepresent invention includes: a polishing platen mounted to be rotatable;a polishing pad fixed on the polishing platen; abrasive supply means forsupplying an abrasive onto the polishing pad; a substrate holder,mounted to be rotatable above the polishing pad, for holding a substrateto be polished and pressing and polishing the substrate against thepolishing pad; a dresser, mounted to be rotatable above the polishingpad, for dressing the polishing pad; torque detection means fordetecting at least one of the rotation torque of the polishing platen,the rotation torque of the substrate holder and the rotation torque ofthe dresser; and dresser control means for increasing at least one ofprocessing parameters including revolving speed of the dresser, pressureof the dresser against the polishing pad and amount of time during whichthe dresser dresses the polishing pad if the rotation torque detected bythe torque detection means is smaller than a predetermined value.

In the second chemical/mechanical polishing apparatus, when clogging isgenerated in the polishing surface of the polishing pad after a certainnumber of substrates have been polished one after another, the rotationtorque detected by the torque detection means becomes smaller than apredetermined value because of the decrease in frictional force betweenthe substrate and the polishing pad. Then, the dresser control meansincreases at least one of the processing parameters including: revolvingspeed of the dresser; pressure of the dresser against the polishing pad;and amount of time during which the dresser dresses the polishing pad.As a result, clogging can be eliminated from the polishing surface ofthe polishing pad and the amount of the abrasive interposed between thesubstrate and the polishing pad can be increased. Accordingly, it ispossible to prevent the polishing rate from decreasing and to eliminatethe variation in polishing rates among the substrates.

The first or second chemical/mechanical polishing apparatus preferablyfurther includes polishing control means for obtaining a rotation torqueintegrated value by integrating the rotation torque detected by thetorque detection means with respect to time, and for stopping theoperation of pressing and polishing the substrate, held by the substrateholder, against the polishing pad when the rotation torque integratedvalue reaches a prescribed value.

In such an embodiment, the variation in polishing amounts among thesubstrates can be reduced because a rotation torque integrated valuecorresponds to a polishing amount of a substrate. As a result, polishingcan be performed just as originally designed.

A first chemical/mechanical polishing method according to the presentinvention includes the steps of: a) rotating a substrate holder, whichholds a substrate thereon, with an abrasive supplied onto a polishingpad fixed on a rotating polishing platen, bringing the substrate down tobe closer to the polishing pad, and then pressing the substrate againstthe polishing pad, thereby polishing the substrate; b) detecting atleast one of the rotation torque of the polishing platen and therotation torque of the substrate holder; and c) dressing the polishingpad if the rotation torque detected in the step b) is equal to orsmaller than a predetermined value.

In the first chemical/mechanical polishing method, when clogging isgenerated in the polishing surface of the polishing pad after a certainnumber of substrates have been polished one after another, the rotationtorque detected in the step b) becomes a predetermined value or lessbecause of the decrease in frictional force between the substrate andthe polishing pad. Then, the polishing pad is dressed. As a result,clogging can be eliminated from the polishing surface of the polishingpad and the amount of the abrasive interposed between the substrate andthe polishing pad can be increased. Accordingly, it is possible toprevent the polishing rate from decreasing and to eliminate thevariation in polishing rates among the substrates.

A second chemical/mechanical polishing method according to the presentinvention includes the steps of: a) rotating a substrate holder, whichholds a substrate thereon, with an abrasive supplied onto a polishingpad fixed on a rotating polishing platen, bringing the substrate down tobe closer to the polishing pad, and then pressing the substrate againstthe polishing pad, thereby polishing the substrate; b) dressing thepolishing pad by pressing a rotating dresser against the polishing pad;c) detecting at least one of the rotation torque of the polishingplaten, the rotation torque of the substrate holder and the rotationtorque of the dresser; and d) increasing at least one of processingparameters including revolving speed of the dresser, pressure of thedresser against the polishing pad and amount of time during which thedresser dresses the polishing pad if the rotation torque detected in thestep c) is smaller than a predetermined value.

In the second chemical/mechanical polishing method, when clogging isgenerated in the polishing surface of the polishing pad after a certainnumber of substrates have been polished one after another, the rotationtorque detected in the step c) becomes smaller than a predeterminedvalue because of the decrease in frictional force between the substrateand the polishing pad. Then, at least one of the processing parametersconsisting of: revolving speed of the dresser; pressure of the dresseragainst the polishing pad; and amount of time during which the dresserdresses the polishing pad is increased. As a result, clogging can beeliminated from the polishing surface of the polishing pad and theamount of the abrasive interposed between the substrate and thepolishing pad can be increased. Accordingly, it is possible to preventthe polishing rate from decreasing and to eliminate the variation inpolishing rates among the substrates.

The first or second chemical/mechanical polishing method preferablyfurther includes the step of obtaining a rotation torque integratedvalue by integrating the rotation torque detected in the step c) withrespect to time, and stopping the operation of polishing the substratein the step a) when the rotation torque integrated value reaches aprescribed value.

In such an embodiment, the variation in polishing amounts among thesubstrates can be reduced because a rotation torque integrated valuecorresponds to a polishing amount of a substrate. As a result, polishingcan be performed just as originally designed.

In the second chemical/mechanical polishing method, if the rotationtorque detected in the step c) is substantially equal to thepredetermined value, the processing parameters are preferably notchanged in the step d).

In such an embodiment, the process can swiftly proceed to dressing onthe polishing pad.

In the second chemical/mechanical polishing method, the step d)preferably includes the step of further increasing the increasedprocessing parameter if the rotation torque detected in the step c) isstill smaller than the predetermined value after the processingparameter has been increased.

In such an embodiment, even if the polishing surface of the polishingpad gets clogged again after polishing on the substrates has furtheradvanced, the polishing surface of the polishing pad can recover itsinitial state. Accordingly, it is possible to prevent the variation inpolishing rates among the substrates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation illustrating an overall arrangementfor a CMP polisher in the first embodiment of the present invention.

FIG. 2 is a waveform chart representing the rotation torque waveforms ofa polishing platen where a plurality of substrates are polished oneafter another in a CMP method of the first embodiment.

FIG. 3 is a schematic representation illustrating an overall arrangementfor a CMP polisher in the second embodiment of the present invention.

FIG. 4 is a schematic representation illustrating an overall arrangementfor a CMP polisher in the third embodiment of the present invention.

FIG. 5 is a schematic representation illustrating an overall arrangementfor a CMP polisher in the fourth embodiment of the present invention.

FIG. 6 is a chart for illustrating a method of integrating rotationtorque values in a CMP method of the fourth embodiment.

FIG. 7 is a chart illustrating the relationship among the respectivetime periods during which dressing and polishing process steps areperformed and the rotation torque during polishing process steps in aCMP method in the fifth embodiment of the present invention.

FIG. 8 is a chart illustrating the relationship between the rotationtorque during polishing process steps and processing time intervals ofdressing process steps in the CMP method of the fifth embodiment.

FIG. 9 is a chart illustrating the relationship between the rotationtorque during polishing process steps and the loads applied in dressingprocess steps in a CMP method in the sixth embodiment of the presentinvention.

FIG. 10 is a schematic representation of a conventional CMP polisher.

FIG. 11 is a waveform chart illustrating the solution principle of thepresent invention and showing the waveform of a rotation torque signalwhere dressing is performed on a polishing pad just before a polishingprocess step is performed on a substrate.

FIG. 12 is a waveform chart illustrating the solution principle of thepresent invention and showing the waveforms of rotation torque signalswhere dressing is performed on a polishing pad just before a polishingprocess step is performed on a substrate and then a plurality ofsubstrates are polished one after another.

FIG. 13 is a graph illustrating the solution principle of the presentinvention and showing the relationship between the number of substratesprocessed and a polishing rate.

DETAILED DESCRIPTION OF THE INVENTION EMBODIMENT 1

Hereinafter, CMP polisher and method in the first embodiment of thepresent invention will be described with reference to FIGS. 1 and 2.

FIG. 1 illustrates an overall arrangement for the CMP polisher of thefirst embodiment. As shown in FIG. 1, a substrate 101 to be polished,made of silicon or the like, is held by a substrate holder 102, which ismounted to be rotatable and vertically movable. A film to be polished,such as a silicon dioxide film, is deposited on the surface of thesubstrate 101. A polishing pad 103 for polishing the film to be polishedon the substrate 101 is attached to the planar surface of a polishingplaten 104 for moving rotationally. An abrasive (in a slurry state) 105is supplied through an abrasive supply tube 106 every time by apredetermined amount and dripped onto the polishing pad 103.

In the CMP polisher of the first embodiment, when the polishing platen104 is rotated with the abrasive 105 dripped through the abrasive supplytube 106 onto the polishing pad 103, the polishing pad 103 is alsorotated correspondingly. And when the substrate holder 102 is broughtdown while rotating, the film to be polished on the substrate 101, heldby the substrate holder 102, comes into contact with the polishing pad103. As a result, the film on the substrate 101 is polished.

Above the polishing pad 103, a dresser 107 is mounted to be rotatableand vertically movable. The dresser 107 comes into contact with thepolishing surface of the polishing pad 103, thereby roughening thepolishing surface of the polishing pad 103 that has got clogged becauseof the attachment of polishing debris and/or abrasive particlescontained in the abrasive. In this manner, the polishing surface of thepolishing pad 103 regains its capacity to hold the abrasive.

The first embodiment is characterized in that a torque detector 108A fordetecting the rotation torque of a rotation axis 104 a of the polishingplaten 104 is secured to the rotation axis 104 a. The torque detector108A continuously detects the rotation torque of the rotation axis 104 aof the polishing platen 104 and outputs the detected rotation torque asa rotation torque signal.

The rotation torque signal output from the torque detector 108A isprovided to a torque monitor 109. The torque monitor 109 quantifies therotation torque signal received, stores the quantified rotation torquesignal as a measured torque value, and compares the measured torquevalue stored to a reference torque value stored beforehand(predetermined value). If the measured torque value is equal to orsmaller than the reference torque value, then the torque monitor 109outputs a torque variation signal. Since the rotation torque detected bythe torque detector 108A represents the roughness of the polishingsurface of the polishing pad 103, the measured torque value quantifiedby the torque monitor 109 represents the quantified roughness of thepolishing surface of the polishing pad 103. For example, if the measuredtorque value is equal to or smaller than the reference torque value,then the polishing surface of the polishing pad 103 has got cloggedbecause of the attachment of polishing debris and/or the mass ofabrasive particles thereto. In other words, it means that the cloggingstate of the polishing surface of the polishing pad 103 has exceeded apredetermined criterion.

A dresser controller 110 for controlling the rotation motion andvertical motion of the dresser 107 is secured to the rotation axis 107 aof the dresser 107. On receiving the torque variation signal as an inputfrom the torque monitor 109, the dresser controller 110 sets theprocessing parameters including revolving speed of the dresser 107,pressure of the dresser 107 against the polishing pad 103, and time ofcontact between the dresser 107 and the polishing pad 103, therebymaking the dresser 107 dress the polishing pad 103.

Hereinafter, it will be specifically described how the dressercontroller 110 controls the dresser 107.

For example, in polishing twenty-five substrates per lot one afteranother, when the polishing pad 103 gets clogged, the torque monitor 109determines that the measured torque value became equal to or smallerthan the reference torque value during polishing of a substrate, e.g., afifth substrate, and outputs a torque variation signal. In response tothe torque variation signal received, the dresser controller 110 setsrevolving speed of the dresser 107, pressure of the dresser 107 againstthe polishing pad 103, and time of contact between the dresser 107 andthe polishing pad 103 at a time when polishing of the substrate inquestion is finished, thereby making the dresser 107 dress the polishingpad 103. After dressing on the polishing pad 103 has been completed andclogging has been eliminated from the polishing pad 103, polishing iscontinuously performed on another remaining substrate, e.g., a sixthsubstrate, included in one lot. By repeatedly performing such a processstep, polishing is performed on the remaining substrates included in onelot by the polishing pad 103, from which clogging has been eliminatedthrough dressing, i.e., the polishing pad 103 that has recovered itsinitial state. Thus, the variation in polishing rates among all thesesubstrates included in one lot can be reduced.

In the first embodiment, the dresser controller 110 controls andinstructs the dresser 107 to perform dressing at a point in time whenpolishing on a current substrate is completed. Alternatively, dressingmay be performed in parallel within a time interval during whichpolishing on the current substrate is being performed.

FIG. 2 illustrates the rotation torque waveforms, detected by the torquedetector 108A for the rotation axis 104 a of the polishing platen 104,where a plurality of substrates have been polished one after another inaccordance with the CMP method of the first embodiment. As can beunderstood from FIG. 2, since the rotation torque waveforms of thesubstrates polished one after another have stabilized amplitudes andshapes, the polishing rates for the respective substrates are also keptconstant.

In the first embodiment, the torque monitor 109 quantifies the rotationtorque signal for the rotation axis 104 a of the polishing platen 104,which signal has been output from the torque detector 108A, as ameasured torque value. If the measured torque value becomes equal to orsmaller than the reference torque value, the torque monitor 109 outputsa torque variation signal. On receiving the torque variation signal fromthe torque monitor 109, the dresser controller 110 makes the dresser 107dress the polishing pad 103. That is to say, when the polishing surfaceof the polishing pad 103 gets clogged, the polishing pad 103 is dressedby the dresser 107. Accordingly, the roughness of the polishing surfaceof the polishing pad 103 is maintained substantially constant. Thus, thevariation in polishing rates among the substrates can be reduced andtherefore polishing can be performed just as originally designed bypolishing each substrate for the same amount of time. As a result, theyield of a chemical/mechanical polishing process on substrates can beincreased.

EMBODIMENT 2

Hereinafter, CMP polisher and method in the second embodiment of thepresent invention will be described with reference to FIG. 3.

FIG. 3 illustrates an overall arrangement for the CMP polisher of thesecond embodiment. In this embodiment, the same members as those of thefirst embodiment shown in FIG. 1 will be identified by the samereference numerals and the description thereof will be omitted herein.

The second embodiment is characterized in that a torque detector 108Bfor detecting the rotation torque of the rotation axis 102 a of thesubstrate holder 102 is secured to the rotation axis 102 a. The torquedetector 108B continuously detects the rotation torque of the rotationaxis 102 a of the substrate holder 102 and outputs the detected rotationtorque as a rotation torque signal. The rotation torque signal outputfrom the torque detector 108B is provided to a torque monitor 109 as inthe first embodiment. If the measured torque value becomes equal to orsmaller than the reference torque value, then the torque monitor 109outputs a torque variation signal. On receiving the torque variationsignal as an input from the torque monitor 109, the dresser controller110 sets revolving speed of the dresser 107, pressure of the dresser 107against the polishing pad 103, and time of contact between the dresser107 and the polishing pad 103, thereby making the dresser 107 dress thepolishing pad 103.

Since the rotation torque detected by the torque detector 108Brepresents the roughness of the polishing surface of the polishing pad103, the measured torque value quantified by the torque monitor 109represents the quantified roughness of the polishing surface of thepolishing pad 103.

In the second embodiment, the torque monitor 109 quantifies the rotationtorque signal for the rotation axis 102 a of the substrate holder 102,which signal has been output from the torque detector 108B, as ameasured torque value. When the measured torque value becomes equal toor smaller than the reference torque value, the torque monitor 109outputs a torque variation signal. On receiving the torque variationsignal as an input from the torque monitor 109, the dresser controller110 makes the dresser 107 dress the polishing pad 103. That is to say,when the polishing surface of the polishing pad 103 gets clogged, thepolishing surface of the polishing pad 103 is dressed by the dresser107. Accordingly, the roughness of the polishing surface of thepolishing pad 103 is maintained substantially constant. Thus, thevariation in polishing rates among the substrates can be reduced andpolishing can be performed just as originally designed. As a result, theyield of a chemical/mechanical polishing process on substrates can beincreased.

In the second embodiment, the dresser controller 110 controls andinstructs the dresser 107 to perform dressing at a point in time whenpolishing on a current substrate is completed. Alternatively, dressingmay be performed in parallel within a time interval during whichpolishing is being performed on the current substrate.

In the second embodiment, a single substrate holder 102 is provided.Alternatively, a plurality of substrate holders 102 may be provided anda plurality of torque detectors 108B, each detecting the rotation torqueof the rotation axis 102 a of an associated one of the substrate holders102, may be secured to the rotation axes 102 a. In such a case, therotation torque signals output from the respective torque detectors 108Bare input to the torque monitor 109. In response thereto, the torquemonitor 109 quantifies the rotation torque signals, which have beenoutput from the respective torque detectors 108B for the rotation axes102 a of the respective substrate holders 102, as measured torquevalues, calculates an average of the measured torque values and outputsa torque variation signal when the average of the measured torque valuesbecomes smaller than the reference torque value.

In such an embodiment, in a batch-type CMP polisher for polishing aplurality of substrates simultaneously, the variation in polishing ratesamong the substrates polished simultaneously can also be reduced.

EMBODIMENT 3

Hereinafter, CMP polisher and method in the third embodiment of thepresent invention will be described with reference to FIG. 4.

FIG. 4 illustrates an overall arrangement for the CMP polisher of thethird embodiment. In this embodiment, the same members as those of thefirst embodiment shown in FIG. 1 will be identified by the samereference numerals and the description thereof will be omitted herein.In the third embodiment, polishing on the substrate 101 and dressing bythe dresser 107 on the polishing pad 103 are supposed to be performedsimultaneously.

The third embodiment is characterized in that a torque detector 108C fordetecting the rotation torque of the rotation axis 107 a of the dresser107 is secured to the rotation axis 107 a. The torque detector 108Ccontinuously detects the rotation torque of the rotation axis 107 a ofthe dresser 107 and outputs the detected rotation torque as a rotationtorque signal. The rotation torque signal output from the torquedetector 108C is provided to a torque monitor 109 as in the firstembodiment. If the measured torque value becomes equal to or smallerthan the reference torque value, then the torque monitor 109 outputs atorque variation signal. On receiving the torque variation signal as aninput from the torque monitor 109, the dresser controller 110 increasesat least one of the processing parameters including: revolving speed ofthe dresser 107; pressure of the dresser 107 against the polishing pad103; and time of contact between the dresser 107 and the polishing pad103, thereby intensifying dressing performed by the dresser 107 on thepolishing pad 103.

Since the rotation torque detected by the torque detector 108Crepresents the roughness of the polishing surface of the polishing pad103, the measured torque value quantified by the torque monitor 109represents the quantified roughness of the polishing surface of thepolishing pad 103.

In the third embodiment, the torque monitor 109 quantifies the rotationtorque signal of the rotation axis 107 a of the dresser 107, whichsignal has been output from the torque detector 108C, as a measuredtorque value. When the measured torque value becomes equal to or smallerthan the reference torque value, the torque monitor 109 outputs a torquevariation signal. On receiving the torque variation signal as an inputfrom the torque monitor 109, the dresser controller 110 increases atleast one of the processing parameters including: revolving speed of thedresser 107; pressure of the dresser 107 against the polishing pad 103;and time of contact between the dresser 107 and the polishing pad 103,thereby intensifying dressing performed by the dresser 107 on thepolishing pad 103. That is to say, when the polishing surface of thepolishing pad 103 gets clogged, the dressing performed by the dresser107 is intensified. Accordingly, the roughness of the polishing surfaceof the polishing pad 103 is maintained substantially constant. Thus, thevariation in polishing rates among the substrates can be reduced andpolishing can be performed just as originally designed. As a result, theyield of a chemical/mechanical polishing process on substrates can beincreased.

EMBODIMENT 4

Hereinafter, CMP polisher and method in the fourth embodiment of thepresent invention will be described with reference to FIGS. 5 and 6.

FIG. 5 illustrates an overall arrangement for the CMP polisher of thefourth embodiment. In this embodiment, the same members as those of thefirst embodiment shown in FIG. 1 will be identified by the samereference numerals and the description thereof will be omitted herein.

In the fourth embodiment, the torque detector 108A for detecting therotation torque of the rotation axis 104 a of the polishing platen 104is secured to the rotation axis 104 a as in the first embodiment. Thetorque detector 108A continuously detects the rotation torque of therotation axis 104 a of the polishing platen 104 and outputs the detectedrotation torque as a rotation torque signal.

The fourth embodiment is characterized in that the rotation torquesignal output from the torque detector 108A is provided not only to thetorque monitor 109, but also to a polishing controller 111. As in thefirst embodiment, if the measured torque value becomes equal to orsmaller than the reference torque value, then the torque monitor 109outputs a torque variation signal. On receiving the torque variationsignal as an input from the torque monitor 109, the dresser controller110 sets revolving speed of the dresser 107, pressure of the dresser 107against the polishing pad 103, and time of contact between the dresser107 and the polishing pad 103, thereby making the dresser 107 dress thepolishing pad 103.

In polishing a plurality of substrates one after another, every timepolishing is performed on each substrate, the polishing controller 111quantifies the input rotation torque signals, integrates the quantifiedrotation torque values with respect to time, stores the integrated valueas a rotation torque integrated value, and compares the stored rotationtorque integrated value to a reference torque value (predeterminedvalue) stored beforehand. When the rotation torque integrated valuereaches the reference torque value, the polishing controller 111 outputsa polishing stop signal 112. The reference torque value storedbeforehand is a value representing that a substrate has been polished byan amount originally designed.

The polishing stop signal 112 output from the polishing controller 111is input to a driver for lifting the substrate holder 102. In responseto the signal 112, the driver lifts the substrate holder 102. As aresult, the substrate 101 held by the substrate holder 102 is taken awayfrom the polishing pad 103 and therefore polishing on the substrate 101is terminated.

In chemical/mechanical polishing, the larger the frictional forcebetween the substrate 101 and the polishing pad 103 is, the larger therotational driving force vector A is. As a result, the rotation torque Tis also increased correspondingly. Therefore, the larger the amplitudeof a rotation torque signal is, the larger the frictional force betweenthe substrate 101 and the polishing pad 103 is. Thus, the polishing ratefor the substrate 101 is also increased correspondingly. The integratedvalue obtained by integrating the quantified rotation torque values withrespect to time represents the amount of material removed from thesubstrate 101 by polishing (hereinafter, such an amount will be referredto as a “polishing amount”).

FIG. 6 illustrates a method for integrating the rotation torque valuesquantified by the polishing controller 111. The polishing controller 111quantifies the rotation torque signals supplied from the torque detector108A, stores the quantified rotation torque values as sample values atpredetermined intervals, and integrates the stored sample values,thereby obtaining a rotation torque integrated value. As shown in FIG.6, the area of the rotation torque signal waveform is calculated as atotal sum of the areas of a plurality of rectangles, each of which isdefined by the predetermined interval and the rotation torque samplevalues for an associated sampling interval. This method is generallycalled a “partitioned quadrature”.

In the fourth embodiment, in polishing a plurality of substrates oneafter another, when the area of the rotation torque signal waveform foreach substrate, i.e., the rotation torque integrated value, reaches thereference torque value stored beforehand, the polishing controller 111outputs the polishing stop signal 112, thereby terminating polishing oneach substrate. Thus, since the variation in polishing amounts among thesubstrates can be reduced with more certainty, polishing can beperformed just as originally designed.

In the fourth embodiment, the rotation torque of the polishing platen104 is detected by the torque detector 108A secured to the rotation axis104 a of the polishing platen 104. Alternatively, the rotation torque ofthe substrate holder 102 may be detected by the torque detector 108Bsecured to the rotation axis 102 a of the substrate holder 102 as in thesecond embodiment. Furthermore, the rotation torque of the dresser 107may be detected by the torque detector 108C secured to the rotation axis107 a of the dresser 107 as in the third embodiment. It is noted that indetecting the rotation torque by the torque detector 108C secured to therotation axis 107 a of the dresser 107, polishing on the substrate 101and dressing on the polishing pad 103 should be performed in parallelwith each other.

EMBODIMENT 5

Hereinafter, a CMP method in the fifth embodiment of the presentinvention will be described with reference to FIGS. 1, 7 and 8. In thefifth embodiment, polishing on a substrate and dressing on the polishingpad are supposed to be performed alternately.

The time intervals during which dressing and polishing are respectivelyperformed and the rotation torque during polishing will be describedwith reference to FIG. 7.

First, before polishing on substrates is started, the polishing platen104 and the polishing pad 103 are rotated and the dresser 107 is broughtdown while rotating, thereby performing initial dressing D₀ on thepolishing pad 103. If the initial dressing D₀ is performed in this way,clogging can be eliminated from the polishing surface of the polishingpad 103 before polishing on the substrates is started. Thus, thepolishing pad 103 gets well ready for polishing on the substrates.

Next, after the dresser 107 has been lifted, a first slurry supplyprocess step S₁ is started on the polishing pad 103. Thereafter, whilethe first slurry supply process step S₁ is continued, a first polishingprocess step P₁ is performed by pressing the substrate 101 held by thesubstrate holder 102 against the polishing pad 103 and at the same time,the first rotation torque T₁ of the polishing platen 104 is detected bythe torque detector 108A. The first rotation torque T₁ is detected asrotation torque in the steady state when the waveform of rotation torqueis flattened. When the first polishing process step P₁ on the substrateis finished, a first rinsing process step R₁ is performed, therebycleaning the polishing pad 103.

Next, a first dressing process step D₁ is performed on the polishing pad103. In this case, since the polishing surface of the polishing pad 103has got clogged only slightly as a result of the first polishing processstep P₁, the time interval of the first dressing process step D₁ is setequal to that of the initial dressing process step D₀.

Then, while a second slurry supply process step S₂ is continued on thepolishing pad 103, a second polishing process step P₂ is performed bypressing the substrate 101 against the polishing pad 103 and the secondrotation torque T₂ of the polishing platen 104 is detected. The secondrotation torque T₂ is also detected as rotation torque in the steadystate. In this case, the value of the second rotation torque T₂ issmaller than that of first rotation torque T₁. This is because thefrictional force between the substrate 101 and the polishing pad 103 hasdecreased since the polishing surface of the polishing pad 103 has gotclogged as a result of the second polishing process step P₂. When thesecond polishing process step P₂ on the substrate is finished, a secondrinsing process step R₂ is performed, thereby cleaning the polishing pad103.

Subsequently, a second dressing process step D₂ is performed on thepolishing pad 103. In this case, since the value of the second rotationtorque T₂ is smaller than that of first rotation torque T₁, it can beseen that the polishing surface of the polishing pad 103 has got cloggedas a result of the second polishing process step P₂. Thus, the timeinterval of the second dressing process step D₂ is set longer than thatof the first dressing process step D₁ without changing the load appliedto the substrate holder 102. As a result, clogging can be eliminatedfrom the polishing surface of the polishing pad 103 and the polishingsurface of the polishing pad 103 can recover its initial state.

Then, while a third slurry supply process step S₃ is continued on thepolishing pad 103, a third polishing process step P₃ is performed bypressing the substrate 101 against the polishing pad 103 and the thirdrotation torque T₃ of the polishing platen 104 is detected. The thirdrotation torque T₃ is also detected as rotation torque in the steadystate. In this case, since the polishing surface of the polishing pad103 has recovered its initial state by extending the time interval ofthe second dressing process step D₂, the value of the third rotationtorque T₃ is larger than that of second rotation torque T₂ andapproximately equal to that of the first rotation torque T₁. When thethird polishing process step P₃ on the substrate is finished, a thirdrinsing process step R₃ is performed, thereby cleaning the polishing pad103.

Next, the rotation torque during polishing process steps and theprocessing time intervals of dressing process steps where a large numberof substrates are polished one after another will be described withreference to FIG. 8.

First, as in the example illustrated in FIG. 7, initial dressing isperformed by the dresser 107 on the polishing pad 103 on the processingconditions that the rotation torque is T_(D0) and the processing timeinterval is t₀, thereby recovering the initial state for the polishingsurface of the polishing pad 103. Thereafter, polishing is performed onthe first substrate and the rotation torque T_(P1) of the polishingplaten 104 is measured. In the following description, the rotationtorque T_(P1) of the polishing platen 104 while the first substrate isbeing polished will be called “initial rotation torque T_(P1)”. Then,post-polishing dressing for the first substrate is performed on theprocessing conditions that the rotation torque is T_(D1) and theprocessing time interval is t₁. In this case, the rotation torque T_(D1)is equal to the rotation torque T_(D0) and the processing time intervalt₁ is equal to the processing time interval t₀.

Next, polishing is performed on the second substrate and simultaneouslythe rotation torque T_(P2) of the polishing platen 104 is measured. Inthis case, since the polishing pad 103 has got clogged, the rotationtorque T_(P2) for the second substrate is smaller than the initialrotation torque T_(P1). Then, post-polishing dressing for the secondsubstrate is performed on the processing conditions that the rotationtorque is T_(D2) and the processing time interval is t₂. In this case,the rotation torque T_(P2) during the polishing process step of thesecond substrate is smaller than the initial rotation torque T_(P1).Thus, in the dressing process step, the rotation torque T_(D2) is setequal to the rotation torque T_(D0) but the processing time interval t₂is set longer than the processing time interval t₁, thereby recoveringthe initial state for the polishing surface of the polishing pad 103.

Subsequently, polishing is performed on the third substrate andsimultaneously the rotation torque T_(P3) of the polishing platen 104 ismeasured. In this case, since the polishing surface of the polishing pad103 has recovered its initial state before the polishing process step onthe third substrate is started, the rotation torque T_(P3) for the thirdsubstrate is substantially equal to the initial rotation torque T_(P1).Then, post-polishing dressing for the third substrate is performed onthe processing conditions that the rotation torque is T_(D3) and theprocessing time interval is t₃. In this case, the rotation torque T_(P3)during the polishing process step of the third substrate issubstantially equal to the initial rotation torque T_(P1). Thus, in thedressing process step, the rotation torque T_(D3) is set equal to therotation torque T_(D0) and the processing time interval t₃ is also setequal to the processing time interval t₂.

Thereafter, polishing on a substrate, measurement of the rotation torqueof the polishing platen 104 and postpolishing dressing are repeatedlyperformed on the fourth substrate and so on. In the remaining processsteps, if the rotation torque of the polishing platen 104 issubstantially equal to the initial rotation torque T_(P1), theprocessing time interval of the post-polishing dressing performed afterthat is set equal to the processing time interval of the previousdressing process step. On the other hand, if the rotation torque of thepolishing platen 104 is smaller than the initial rotation torque T_(P1),the processing time interval of the post-polishing dressing performedafter that is set longer than that of the previous dressing processstep, thereby recovering the initial state for the polishing surface ofthe polishing pad 103.

For example, as shown in FIG. 8, if the rotation torque T_(P4) of thepolishing platen 104 during the polishing process step on the fourthsubstrate is substantially equal to the initial rotation torque T_(P1),the processing time interval t₄ of post-polishing dressing for thefourth substrate is set equal to the processing time interval t₃ ofpost-polishing dressing for the third substrate. In general, if therotation torque T_(Pn) of the polishing platen 104 during the polishingprocess step on the n-th substrate is smaller than the initial rotationtorque T_(P1), the processing time interval t_(n) of post-polishingdressing for the n-th substrate is set longer than that of the previousdressing process step. And if the rotation torque T_(Pn+1) of thepolishing platen 104 during the polishing process step on the (n+1)thsubstrate is substantially equal to the initial rotation torque T_(P1),the processing time interval t_(n+1) of post-polishing dressing for the(n+1)th substrate is set equal to the processing time interval t_(n) ofpost-polishing dressing for the n-th substrate.

In the fifth embodiment, if the rotation torque of the polishing platen104 during a polishing process step on a substrate is substantiallyequal to the initial rotation torque T_(P1), the processing timeinterval of a dressing process step performed after that is set equal tothat of the previous dressing process step. On the other hand, if therotation torque of the polishing platen 104 is smaller than the initialrotation torque T_(P1), it can be seen that the polishing surface of thepolishing pad 103 has got clogged. Thus, the processing time interval ofthe dressing process step performed after that is set longer than thatof the previous dressing process step without changing the load appliedon the substrate holder 102 and the respective revolving speeds of thesubstrate holder 102 and the polishing platen 104, thereby recoveringthe initial state for the polishing surface of the polishing platen 104.Accordingly, the polishing rates among the substrates can be keptconstant.

In the fifth embodiment, the processing conditions of dressing are setbased on the rotation torque of the rotation axis 104 a of the polishingplaten 104. Alternatively, the processing conditions of dressing may beset based on the rotation torque of the rotation axis 102 a of thesubstrate holder 102.

Also, in this embodiment, the processing conditions for dressing arechanged by extending a processing time interval. Alternatively, thepressure against the dresser 107, the revolving speed of the dresser107, the revolving speed of the polishing platen 104 or a combinationthereof may also be increased.

EMBODIMENT 6

Next, a CMP method in the sixth embodiment of the present invention willbe described with reference to FIGS. 1 and 9. In the sixth embodiment,polishing on a substrate and dressing on the polishing pad are supposedto be performed in parallel with each other.

Hereinafter, the relationship between rotation torque during a polishingprocess step and load (pressure) during a dressing process step where alarge number of substrates are polished one after another will bedescribed with reference to FIG. 9. It is noted that the processing timeintervals are set constant in the sixth embodiment for the respectivedressing process steps.

First, initial dressing is performed on the polishing pad 103 with theapplication of load G₀ to the dresser 107, thereby recovering theinitial state for the polishing surface of the polishing pad 103.Thereafter, while the first polishing process step is being performed ona substrate, the rotation torque T_(P1) of the polishing platen 104 ismeasured. And at the same time, the first dressing process step isperformed on the polishing pad 103 with load G₁ applied on the dresser107. The load G₁ for the first dressing process step is set equal to theload G₀ for initial dressing. It is noted that the rotation torqueT_(P1) of the polishing platen 104 during the first polishing processstep will be called “initial rotation torque T_(P1)”.

Then, while the second polishing process step is being performed onanother substrate, the rotation torque T_(P2) of the polishing platen104 is measured. And at the same time, the second dressing process stepis performed on the polishing pad 103 with load G₂ applied on thedresser 107. In this case, since the rotation torque during the firstpolishing process step is the initial rotation torque T_(P1), the loadG₂ for the second dressing process step is set equal to the load G₁ forthe first dressing process step. On the other hand, the rotation torqueT_(P2) during the second polishing process step is smaller than theinitial rotation torque T_(P1).

Subsequently, while the third polishing process step is being performedon another substrate, the rotation torque T_(P3) of the polishing platen104 is measured. And at the same time, the third dressing process stepis performed on the polishing pad 103 with load G₃ applied on thedresser 107. In this case, since the rotation torque T_(P2) during thesecond polishing process step is smaller than the initial rotationtorque T_(P1), the load G₃ for the third dressing process step is setlarger than the load G₂ for the second dressing process step by ΔG,thereby recovering the initial state for the polishing surface of thepolishing pad 103.

Thereafter, while the fourth polishing process step is being performedon another substrate, the rotation torque T_(P4) of the polishing platen104 is measured. And at the same time, the fourth dressing process stepis performed on the polishing pad 103 with load G₄ applied on thedresser 107. In this case, since the rotation torque T_(P3) during thethird polishing process step is substantially equal to the initialrotation torque T_(P1), the load G₄ for the fourth dressing process stepis set equal to the load G₃ for the third dressing process step. Sincethe polishing surface of the polishing pad 103 has recovered its initialstate by setting the load G₃ for the third dressing process step largerthan the load G₂ for the second dressing process step, the rotationtorque T_(P4) during the fourth polishing process step is substantiallyequal to the initial rotation torque T_(P1)

Thereafter, the rotation torque of the polishing platen 104 isrepeatedly measured while performing the fifth polishing process stepand so on for remaining substrates. And at the same time, dressing isalso repeatedly performed with load applied on the dresser 107. Ingeneral, if the rotation torque of the polishing platen 104 issubstantially equal to the initial rotation torque T_(P1), the load forthe next dressing process step is set equal to the load for the currentdressing process step. On the other hand, if the rotation torque of thepolishing platen 104 is smaller than the initial rotation torque T_(P1),the load for the next dressing process step is set larger than the loadfor the current dressing process step, thereby recovering the initialstate for the polishing surface of the polishing pad 103.

For example, as shown in FIG. 9, if the rotation torque T_(Pn) of thepolishing platen 104 during the n-th polishing process step on asubstrate is smaller than the initial rotation torque T_(P1), the loadG_(n+1) for the (n+1)th dressing process step is set larger than theload G_(n) for the n-th dressing process step by ΔG′, thereby recoveringthe initial state for the polishing surface of the polishing pad 103.

In the sixth embodiment, if the rotation torque of the polishing platen104 during a polishing process step on a substrate is substantiallyequal to the initial rotation torque T_(P1), the load for the nextdressing process step is set equal to the load for the current dressingprocess step. On the other hand, if the rotation torque of the polishingplaten 104 is smaller than the initial rotation torque T_(P1), it can beseen that the polishing surface of the polishing pad 103 has gotclogged. Thus, the load for the next dressing process step is set largerthan the load for the current dressing process step, thereby recoveringthe initial state for the polishing surface of the polishing pad 103. Asa result, the polishing rates among the substrates can be kept constant.

In the sixth embodiment, the processing conditions for dressing are setbased on the rotation torque of the rotation axis 104 a of the polishingplaten 104. Alternatively, the processing conditions for dressing may beset based on the rotation torque of the substrate holder 102 or therotation torque of the dresser 107.

In the fifth and sixth embodiments, rotation torque in the steady statewhere the rotation torque waveform has flattened is detected during apolishing process step. Alternatively, rotation torque immediately aftera polishing process step is started, i.e., a peak value of rotationtorque, may be detected instead. Such a method is particularly effectiveto polishing a soft film such as a BPSG film within a short period oftime, i.e., a case where polishing is likely to be completed beforerotation torque has settled in the steady state.

Also, in the fifth and sixth embodiments, the rotation torque during thefirst polishing process step performed after the polishing surface ofthe polishing pad 103 has recovered its initial state through initialdressing is regarded as initial rotation torque. Alternatively, rotationtorque obtained beforehand by experiment or calculation may be used aspreset rotation torque, and measured rotation torque may be compared tothe preset rotation torque.

What is claimed is:
 1. A chemical/mechanical polishing method comprisingthe steps of: a) rotating a substrate holder, which holds a substratethereon, with an abrasive supplied onto a polishing pad fixed on arotating polishing platen, bringing the substrate down to be closer tothe polishing pad, and then pressing the substrate against the polishingpad, thereby polishing the substrate; b) detecting at least one of therotation torque of the polishing platen and the rotation torque of thesubstrate holder; and c) dressing the polishing pad if the rotationtorque detected in the step b) is equal to or smaller than a firstrotational torque value.
 2. The method of claim 1, further comprisingthe step of obtaining a rotation torque integrated value by integratingthe rotation torque detected in the step b) with respect to time, andstopping the operation of polishing the substrate in the step a) whenthe rotation torque integrated value reaches said first rotationaltorque value.
 3. A chemical/mechanical polishing method comprising thesteps of: a) rotating a substrate holder, which holds a substratethereon, with an abrasive supplied onto a polishing pad fixed on arotating polishing platen, bringing the substrate down to be closer tothe polishing pad, and then pressing the substrate against the polishingpad, thereby polishing the substrate; b) dressing the polishing pad bypressing a rotating dresser against the polishing pad; c) detecting atleast one of the rotation torque of the polishing platen, the rotationtorque of the substrate holder and the rotation torque of the dresser;and d) increasing at least one of processing parameters includingrevolving speed of the dresser, pressure of the dresser against thepolishing pad and amount of time during which the dresser dresses thepolishing pad if the rotation torque detected in the step c) is smallerthan a first rotational torque value.
 4. The method of claim 3, furthercomprising the step of obtaining a rotation torque integrated value byintegrating the rotation torque detected in the step c) with respect totime, and stopping the operation of polishing the substrate in the stepa) when the rotation torque integrated value reaches said firstrotational torque value.
 5. The method of claim 3, wherein in the stepd), if the rotation torque detected in the step c) is substantiallyequal to the first rotational torque value, the processing parametersare not changed.
 6. The method of claim 3, wherein the step d) comprisesthe step of further increasing the increased processing parameter if therotation torque detected in the step c) is still smaller than the firstrotational torque value after the processing parameter has beenincreased.